He was the runner-up in men's singles at the Japanese National Championships in 2006 when he lost the final against Satoshi Iwabuchi.

When he played at the 2019 Shenzhen Longhua Open against 18-year-old Chun-hsin Tseng as a lucky loser, it was the largest age difference ever in a Challenger match, with Matsui being the oldest player at 41 years old, with an ATP ranking.

Plus Matsui participated in the first 2 editions of ATP Cup in 2020–2021 as a member of Team Japan.

In February 2024, Matsui achieved his highest ranking in doubles, No.123, at the age of 45; he later improved this to No.

[4] (Men's Doubles 2005,2022) Based in Kashiwa,[8] Matsui speaks Japanese and English fluently.